The present invention relates to deicing compositions having additives which minimize the spalling of concrete.
Due to its availability and low cost, sodium chloride is by far the most widely used material for deicing roads, sidewalks, etc. A major, well-known problem with sodium chloride as a deicer is its effect on concrete. The use of sodium chloride as a deicer is known to greatly hasten the scaling or spalling of concrete, necessitating early repair or replacement of concrete structures. Other known deicing compounds, such as magnesium chloride, calcium chloride, potassium chloride and urea are also known to spall concrete.
Attempts have been made to formulate deicing compositions with various additives in order to reduce the spalling effect of sodium chloride on concrete. U.S. Pat. No. 4,094,805, issued to Hansen, describes the admixture of high molecular weight polyethylene oxide with sodium chloride. To the best of applicants' knowledge, such a composition has never been commercialized, at least to any significant degree. In their own tests of polyethylene oxide with sodium chloride as a deicer, applicants have found that this polymer tends to make a surface slippery which would tend to make it unsuitable for use on roads or sidewalks. Furthermore, the high price of this polymer would tend to make its use prohibitive in a deicing composition to be spread on concrete. Polyethylene oxide was also found to be less effective than compositions of the present invention described herein.
Subsequent U.S. Pat. No. 4,148,938, also issued to Hansen, describes the addition of carboxymethyl cellulose, an anionic polymer, to sodium chloride to prevent spalling of concrete. Carboxymethyl cellulose is a gelling agent and it is believed that its action is to pick up moisture and swell so as to close pores in concrete and create a partial seal against moisture and brine. It is explained, however, in this patent that in addition to the carboxymethyl cellulose, a "protecting agent", generally soda ash (Na.sub.2 CO.sub.3), must be added. Otherwise, calcium ions that are available in the concrete react with the carboxyl groups of the carboxymethyl cellulose, precipitating and rendering ineffective the same. Such compositions have been commercialized on a limited basis. A major drawback to such a composition is the inclusion of soda ash or other highly alkaline, sodium-containing "protecting agent" which poses some danger to users of the composition, particularly if the composition or the brine resulting therefrom comes in contact with sensitive tissues, e.g., the eyes. Some jurisdictions are presently considering requiring a composition containing soda ash to be labeled as a potentially hazardous material.